Recently, as the printing method for performing high speed recording method, the ink jet method has been frequently utilized. This ink jet method is a method which performs printing on a recording paper by permitting ink jetted out through a nozzle, mesh-like film or slit, and generally as the ink, there has been used one comprising a dye or pigment which is the colorant, additive such as wetting agent, dissolving aid, pH controller, preservative, etc., and water or an organic solvent, and containing generally 1 to 10 wt % of the colorant.
Since a coated paper such as silica-coated paper, etc. used as a recording paper is expensive, it is desirable to use a plain paper. However, when recording is performed on a plain paper by use of an aqueous ink, because of slow penetration of aqueous ink, troubles are involved in the case of performing high speed recording, full color recording with much ink amount, etc., whereby no good printing could be done. For solving such problems, it becomes necessary (i) to remove the solvent by use of dryer, or (ii) to promote penetration of the ink into the paper by lowering the surface tension of the ink. In the case of (i), however, power is required, whereas in the case of (ii), there is the problem that the printed dot image is blurred.
The present invention has been accomplished under the state of the art as described above.